Remove API's reliance on overwriting sys.argv (#2908)

ambv · JukkaL · commit 5230327eac96 · 2017-03-06T14:40:48.000Z
* Remove API's reliance on overwriting sys.argv

Also, original `sys.stdout` and `sys.stderr` are now recovered also in case of
internal exceptions.

Test plan:

- mypy command-line still works

- all tests still pass
diff --git a/mypy/api.py b/mypy/api.py
@@ -41,9 +41,7 @@
 from mypy.main import main
 
 
-def run(params: List[str]) -> Tuple[str, str, int]:
-    sys.argv = [''] + params
-
+def run(args: List[str]) -> Tuple[str, str, int]:
     old_stdout = sys.stdout
     new_stdout = StringIO()
     sys.stdout = new_stdout
@@ -53,12 +51,12 @@ def run(params: List[str]) -> Tuple[str, str, int]:
     sys.stderr = new_stderr
 
     try:
-        main(None)
+        main(None, args=args)
         exit_status = 0
     except SystemExit as system_exit:
         exit_status = system_exit.code
-
-    sys.stdout = old_stdout
-    sys.stderr = old_stderr
+    finally:
+        sys.stdout = old_stdout
+        sys.stderr = old_stderr
 
     return new_stdout.getvalue(), new_stderr.getvalue(), exit_status
diff --git a/mypy/main.py b/mypy/main.py
@@ -24,19 +24,23 @@
 PY_EXTENSIONS = tuple(PYTHON_EXTENSIONS)
 
 
-def main(script_path: str) -> None:
+def main(script_path: str, args: List[str] = None) -> None:
     """Main entry point to the type checker.
 
     Args:
         script_path: Path to the 'mypy' script (used for finding data files).
+        args: Custom command-line arguments.  If not given, sys.argv[1:] will
+        be used.
     """
     t0 = time.time()
     if script_path:
         bin_dir = find_bin_directory(script_path)
     else:
         bin_dir = None
     sys.setrecursionlimit(2 ** 14)
-    sources, options = process_options(sys.argv[1:])
+    if args is None:
+        args = sys.argv[1:]
+    sources, options = process_options(args)
     serious = False
     try:
         res = type_check_only(sources, bin_dir, options)
